Mackie et al.: Variability in reproductive development of Spanish mackerel (Scomberomorus commerson) 



349 



A Pilbara 



C West Coast 



Month 



r i 



Resling (F 2) I I Developing (F3| 



Pre-spawn (F5a) f7 \\1 Post spawning (F5c) 



Developed (F4) 

 Spenl(F6) 



Water temp 



Figure 4 



Annual cycle of Scomberomorus commerson reproduction in Western 

 Australia for (A) Pilbara, (Bl Kimberley, and (Cl West Coast regions, 

 as indicated by histologically staged ovaries. Mid-month sea surface 

 temperatures are overlaid (solid line) and sample sizes are shown above 

 each column. 



The annual reproductive cycle of ovaries in the 

 Kimberley region follows a similar pattern to that in 

 the Pilbara region (Figs. 3 and 4). However, because 

 30-50% of females captured in Kimberley waters dur- 

 ing September 1999 and 2000 were actively spawning, 

 it appears that S. commerson commence spawning at 

 least one month earlier in this region. About 60% of 

 females were also spawning when sampled during Oc- 

 tober 1999 and 2000, although only 35% were spawning 

 during this month in 2001. If spawning in the Kim- 

 berley region commenced in August and concluded in 

 November (same duration as in the Pilbara region), the 

 associated SST ranged from approximately 26.5-27°C 



to 29-30°C (annual maximum approx 30-31 c C; Figs. 

 3 and 4). Sampling of developed ovaries in March also 

 indicated that the reproductive period for S. commerson 

 in the Kimberley region may be more protracted than 

 in the Pilbara region. 



In the West Coast region few reproductively devel- 

 oped ovaries and no spawning ovaries were obtained; 

 S. commerson are rarely captured in this region dur- 

 ing the peak spawning period observed in the northern 

 regions. The maximum sea surface temperature (SST) 

 in this region of around 28°C is above the lower tem- 

 perature range of spawning in the two northern regions. 

 Reproductively developed ovaries obtained from the 



